The present invention relates to a structurally hermetic, light construction concrete which may be reinforced and comprises cement and water and inorganic light weight admixtures compatible with concrete and foamed or bloated to be approximately spherical or ellipsoidal shaped aggregates and in proportions approximately corresponding to the sieve characteristic.
By "in proportions approximately corresponding to the sieve characteristic" is meant the proportions of varying grain sizes in the mixture of additives corresponding to FIG. 2 of German Industrial Standard DIN 1045. In FIG. 2 of DIN 1045, the proportions of varying grain size are: 3 to 18 percent by weight passes through 0.25 mm mesh, 12 to 49 percent by weight passes through 1.0 mm mesh, 21 to 62 percent by weight passes through 2.0 mm mesh, 36 to 74 percent by weight passes through 4.0 mm mesh, 60 to 88 percent by weight passes through 8.0 mm mesh, and 100 percent by weight passes through 16.0 mm mesh.
The state of the art of raw material as used in the present invention may be ascertained by reference to the Kirk-Othmer "Encyclopedia of Chemical Technology", 2nd Ed. (1964), Vol. 4, pages 684-710, under the section "Cement", and by reference to U.S. Pat. Nos. 3,184,371 of Seidl; 3,261,894 of Seidl; 3,652,310 of Kraemer et al.; and 3,814,614 of Kraemer et al., which issued May 18, 1965; July 19, 1966; Mar. 28, 1972; and June 4, 1974, respectively. These disclosures are incorporated herein.
Construction light weight concrete must be structurally hermetic in order to ensure corrosion resistance of any reinforcement. For dry densities less than 1 kg/dm.sup.3 (kilogram per cubic decimeter for a water; cement ratio of 0.25), it should be endowed with as much compressive strength and heat insulation as possible so as to secure the prescribed properties of the various climatic zones for wall thicknesses of 20 .+-. 5 cm in monolithic construction.
U.S. Pat. No. 3,814,614 discloses a structural light weight concrete having a filler/cement weight ratio of about (350 .+-. 100): 650 .+-. 300) and a water/cement weight ratio of about 0.65 .+-. 0.25, the improvement comprising light weight fillers comprising:
(A) STRONGLY ABSORBENT, FOAMED, ALKALI METAL SILICATE GLASS, CONCRETE-COMPATIBLE PRODUCTS OF A SMOOTH UNBROKEN SURFACE, OF AN APPROXIMATELY SPHERICAL OR ELLIPSOIDAL SHAPE IN GRAIN SIZES OF 0.1-6 MM., PREFERABLY 0.1-4.0 MM., AND BULK DENSITIES OF 0.15 .+-. 0.10 KILOGRAMS PER CUBIC DECIMETER, AND
(B) VERY HARD, LOW ABSORBENT, FOAMED OR BLOATED OR OTHERWISE MADE POROUS INORGANIC LIGHT WEIGHT ADDITIVES IN GRAIN SIZES OF 4-25 MM. AND BULK DENSITIES OF 0.6 .+-. 0.2 KILOGRAMS PER CUBIC DECIMETER, WHEREIN THE VOLUME RATIO OF (A) TO (B) IS ABOUT 1:9 TO 9:1.
The light weight construction concretes of U.S. Pat. No. 3,814,614 are processed in conformity with conventional concrete technology and have compressive strengths of 80-250 kp/cm.sup.2 as measured by DIN (German Industrial Standard) 1164 and thermal conductivities .lambda.(measured at 20.degree. C.) of 0.30 to 0.43 kcal/meter-hour.degree. C. for dry densities of 0.92 to 1.14 kg/dm.sup.3.
Mention is further made that the compressive strength of light weight construction concrete mostly depends on the grain strength of the coarse admixtures and less on that of the fine admixtures. However, this prior art patent fails to recognize that the compressive strength of light weight construction concrete for constant cement and water content is a function of grain strength and grain density increasing with increasing grain diameter. This concept generally has been ignored when making light weight construction concrete. Grain strength and grain density of the admixtures employed by the prior art to date decrease with increasing grain size within the sieve characteristic line. Furthermore, it was not known that the conventional concrete technology will not affect the compressive strength of a light weight construction concrete for grain sizes between 0.06 and 0.2 mm. Because of their predominantly crystalline nature, they appreciably reduce thermal resistance while undesirably raising the density.